The present invention relates to a curable composition comprising a photochromic compound and to a cured product thereof. More specifically, it relates to a curable composition which provides a photochromic cured product suitable for use as a spectacle lens or the like and to the cured product.
Photochromism is a reversible phenomenon that a certain compound changes its color immediately upon exposure to light including ultraviolet rays, such as sunlight or light from a mercury lamp and returns to its original color when it is placed in the dark by stopping exposure and is now applied in various fields.
For example, photochromism is applied in the field of spectacle lenses. A plastic lens having photochromism is obtained by curing a polymerizable monomer blended with a photochromic compound having the above property. Fulgimide compounds, spirooxazine compounds, chromene compounds and the like have been discovered as photochromic compounds which can be advantageously used in the above field.
However, when these photochromic compounds are dispersed in a polymer, color density becomes lower, or color development speed and fading speed, particularly fading speed becomes lower than when the compounds are dissolved in a solvent. Therefore, a photochromic cured product which retains the essential properties of a photochromic compound is not obtained yet.
The inventors of the present invention consider that the above phenomenon is caused by the fact that the free space where the molecules of a photochromic compound can move freely is much smaller in a matrix such as a polymer than in a solution because the phenomenon is especially marked in a photochromic compound having a large molecular size. They have proposed a curable composition which has a wide free space in the matrix of cured product as a curable composition free from the above problem (WO 01/05854). They have succeeded in obtaining a desired effect by combining a generally used polymerizable monomer and a polyfunctional polymerizable monomer having at least three polymerizable groups as radically polymerizable monomers in the above curable composition.
However, it has been found that when xe2x80x9ca hard coat to be cured by a condensation methodxe2x80x9d, which is now generally used for plastic lenses, is applied to the surface of a cured product of the above curable composition, the adhesion of the hard coat lowers.
It is an object of the present invention to provide a curable composition capable of providing a photochromic cured product which shows excellent photochromism such as high color density and high fading speed and has excellent adhesion between a matrix and the aforementioned hard coat.
It is another object of the present invention to provide a curable composition which has the above performance and excellent releasability when its cured product is to be removed from a mold such as a glass mold after polymerization.
It is still another object of the present invention to provide a photochromic cured product having the above excellent characteristic properties.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a curable composition comprising:
(A) a polyfunctional radically polymerizable monomer having at least three polymerizable groups in the molecule;
(B) a radically polymerizable monomer having a silanol group or a group capable of forming a silanol group by hydrolysis;
(C) another radically polymerizable monomer different from the above components (A) and (B); and
(D) a photochromic compound, wherein the above components (A) (B) and (C) are contained in amounts of 1 to 50 wt %, 0.5 to 20 wt % and 30 to 98.5 wt % based on the total of the components (A), (B) and (C), respectively, and the above component (D) is contained in an amount of 0.0001 to 10 parts by weight based on 100 parts by weight of the total of the above components (A), (B) and (C).
According to the present invention, secondly, the above objects and advantages of the present invention are attained by a photochromic cured product as a cured product of the curable composition of the present invention.